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| Home > Publications database > Elektronische und ionische Leitfähigkeit von SrCeO$_{3}$ in reduzierender Atmosphäre |
| Book/Report | FZJ-2019-01721 |
1996
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/22041
Report No.: Juel-3318
Abstract: The cerates, doped with trivalent rare earth ions, exhibits remarkable high protonic conductivity in wet and hydrogen containing atmospheres and at temperatures between 600°C-900°C, which are interesting for various applications like fuel cells and gas sensors. The generation of electronic defects under high and very low oxygen partial pressures leads to an increase of the electronic conductivity under this conditions and limit the performance of technical devices. The main attention was therefore focused on the investigation and separation of the partial conductivities. In order to characterise the electronic conduction, measurements using selective blocking electrodes to separate the ionic and the electronic partial conductivity has been applied. The used technique equals a Hebb-Wagner polarisation experiment.The aim of our investigation was the analysis of the eonditions in dry and wet hydrogen and oxygen atmospheres in the temperature range of 700-900°C, corresponding to the extreme requirements by operating a fuel cello The rnain results can be sumrnarised as follow: In hydrogen containing atmospheres, corresponding to low oxygen partial pressures, the ionie and electronic conductivities are of the same magnitude and show a similar dependence only on the equilibrium hydrogen partial pressure. The results can be explained by applying a simple defect model with H$^{\bullet}$ and e' as the dominant defects. On the other side, at high oxygen partial pressure the hole conductivity increase and overwhelms the nearly constant ionic conductivity. Also in this case, applying a simple defect model for the water incorporation and the oxygen-Ioss/incorporation explain the results. In addition, the chemical diffusion coefficients of hydrogen and oxygen vacancies are determined from the polarisation and depolarisation process. With magnetic measurements and from infrared absorption spectroscopy the defect concentration of e' and H$^{\bullet}$ is estimated, enable us to calculate the mobilities of the involved defects.
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